A diode-pumped solid state laser generally comprises a laser diode as the pump source and a laser cavity formed by a laser gain crystal and two reflective mirrors. The laser cavity may further comprise a nonlinear crystal for optical frequency conversion. The performance of the laser, such as its output power, noise level, and mode pattern, is very sensitive to environmental temperature variations. Thus, the laser can only operate within a narrow temperature range, beyond which the power of the laser may drop quickly or overshoot outside the safety limit. The noise level and the mode pattern of the laser may also degrade greatly.
This problem is addressed in the prior art by using thermal control systems, including those active cooling/heating systems that employ thermo-electronic coolers, or those passive cooling systems that employ fluid/air coolants or phase change materials. Some examples can be found in U.S. Pat. No. 5,181,214, ‘Temperature Stable Solid-State Laser Package’ disclosed by Berger et al., U.S. Pat. No. 6,101,201, ‘Solid state laser with longitudinal cooling’ disclosed by Hargis et al., and U.S. Pat. No. 6,570,895, ‘Laser systems using phase change material for thermal control’ disclosed by Heberle.
However, the incorporation of the thermal control system makes the laser cumbersome in size and/or high in power consumption, which is not suitable for some applications such as portable and battery powered laser modules for search and rescue signaling, field measurement instruments, and laser pointers, etc.